How do we know the centre of the earth is Iron?

Question

Like how are scientists 100% sure when we’ve never dug that far down

Thanks in advance

In: 23

Answer 1

There are a number of clues:

* The majority of the Earth is hot enough to be molten (i.e. liquid). As you can see [here](https://scx1.b-cdn.net/csz/news/800a/2015/whataretheea.jpg) the crust with the continents on it is actually very thin, comparatively, and the interior is liquid rock and other materials. In a liquid, it makes sense that metals, which are denser/heavier than rocks, will sink to the center, because of gravity.

* Gravity itself; how much gravity we feel depends on the mass of the Earth. So we know the mass of the Earth from its gravity, and we’ve measured the diameter of the Earth (and its volume). So we can calculate the density of the Earth, and the density indicates that there’s something *heavier / denser than rock* at the center.

* Several metals are denser than rock, but the Earth has a magnetic field, and from our current understanding of magnetism, the core has to be iron (and/or with nickel mixed in) and not something like gold or copper or other metals that do NOT produce magnetism.

So basically it’s an “educated” guess.